I don't think you bought much in Saxon times, not on a village level anyway. Houses (huts) were built specifically for the incoming population, and boats would have been a shared resource, particularly longboats which your average villager inland wouldn't have seen anyway. Military service to the ruling earl was required, and in return you got citizenship which gave you a voice in the councils. For your daily requirements you farmed your own little patch and also farmed for the whole village; you'd have kept a pig and maybe a few chickens if you were lucky. You made your own furniture, and maybe traded your surplus for the occasional piece of jewellery, which would have been VERY rare! I imagine that silver coins were mostly used by higher level Saxons & Vikings in return for large transactions, such as building longboats and equipping an army, or building large communal structures like bridges and churches.